let a:string = 'hello'
type A = string
let a1:A = 'hello'

//基本类型
//string, number, boolean, null, undefined, symbol, bigint
let b1:string = 'hello'
let b2:number = 123
let b3:boolean = true
let b4:null = null
let b5:undefined = undefined
let b6:symbol = Symbol()
let b7:bigint = 123n

//对象类型
//[] , {} , function(){}
let c1:[] = []
let c2:{} = {}
let c3:()=>void = ()=>{}

//ts新增类型
//any, unknown, void, never, enum,
let d1:any = 'hello'
let d2:unknown = 'hello'
let d3:void = undefined

//永不存在的值
let d4:never = (()=>{
    throw new Error('error')
})()

enum E {
    A,
    B,
    C
}


